This invention relates to polyimide copolymers prepared by reacting of a mixture of dianhydrides with a diamine. More specifically, it relates to polyimide polymers prepared from diamines that contain the trifluoromethyl group.
Dianhydrides can be reacted with diamines to form polyimide resins. The formation of the polymer is a two step process. In the first step, the dianhydride reacts with the diamine to form a polyamic acid which generally remains in solution. The polyamic acid solution is then subjected to a curing process which may include heat. If heat is used the solvent evaporates, and the polyamic acid releases water to form the final polyimide. Chemical methods of curing are also available.
There are several methods for forming objects from polyimides. For example, the polyamic acid solution can be spread on a surface and cured to form a film. The surface need not be flat. Alternatively, the polyamic acid solution can be cured to form the polyimide which can then be subjected to heat and pressure to form objects.
Polyimides were first prepared by T. M. Bogert, et al. J. Am. Chem. Soc. 30, 1140 (1908).
U.S. Pat. No. 2,710,853 discloses polyimides based upon pyromellitic acid.
U.S. Pat. No. 3,179,614 discloses polyimides based upon organic diamines that contain aromatic groups bridged by oxygen, nitrogen, sulfur, silicone, and phosphorus.
U.S. Pat. No. 4,876,329 discloses polyimides based upon 3,5-diaminobenzotrifluoride and aromatic dianhydrides such as pyromellitic dianhydride, biphenyl dianhydride, diphenylether dianhydride, benzophenone dianhydride, 2,2-bis(3,4-dicarboxyphenyl)propane dianhydride and 2,2-bis(3,4-dicarboxyphenyl)dianhydride.
U.S. Pat. No. 4,760,126 discloses polyimides based upon fluorine containing diamines such as 2,2-bis[4-aminophenyl]hexafluoropropane with an extremely wide variety of dianhydrides.
The synthesis of 2,2'-oxy-bis[5-(trifluoromethyl)benzenamine] and 4,4'-oxy-bis[3-(trifluoromethyl)benzenamine] is disclosed in J. Am. Chem. Soc. 78, 6034 (1956). The synthesis of 4,4'-thio-bis[3-(trifluoromethyl)benzenamine] and 4,4'-sulfonyl-bis[3-(trifluoromethyl)benzenamine] are reported in J. Am. Chem. Soc. 73, 5125 (1958).